The point of diagnosis, as I understand it, is for a few reasons. 1) Insurance. 2) Communication between healthcare providers. 3) Treatment. 4) Possibly to help you communicate your experiences with people close to you like family.

If none of those are practical or helpful to you, then there's no point in it IMO. Otherwise it could be rather helpful. It's not really supposed to be like in high school where people wore labels like jock or nerd. That's often how people can see it though, so the negative association is understandable. Of course there is the potential for that to happen and it does, all said.

As to there being such little activity on the SPD page, I think it's two-fold. One reason being as you guessed. Also, I don't think there are too many with the DX on this particular site. If they are, they have other things going on where they post more (like depression or dissociation). That's my guess.